Humphris et al. identified four MMR-D tumors (from 385 PC cases), all of which exhibited distinct mechanisms of somatic inactivation of MLH1 and MSH2; however, the authors noted that in their cohort, germline variants did not contribute to the MMR deficiency even in those with familial PC or a personal or family history of Lynch-related tumors [29]. The gene discussed is MLH1; the disease is pachyonychia congenita.